The present invention relates to aqueous solutions or formulations and methods for controlling the growth of microorganisms on a variety of mediums, substrates and in liquid systems. More particularly, the invention relates to using monochloramine and peracid, such as peracetic acid, in aqueous treatment solutions.
Many industrial materials and media when wet or subjected to treatment in water are susceptible to bacterial, fungal, and/or algal deterioration or degradation. A large variety of commercial, industrial, agricultural, and wood materials or products are subject to microbiological attack or degradation which reduces or destroys their economic value. These industrial materials and media include, but are not limited to, for example, wood pulp, wood chips, lumber, adhesives, coatings, animal hides, paper mill liquors, pharmaceutical formulations, cosmetic formulations, toiletry formulations, geological drilling lubricants, petrochemicals, agrochemical compositions, paints, leathers, plastics, seeds, plants, wood, metalworking fluids, cooling water, recreational water, influent plant water, waste water, pasteurizers, retort cookers, tanning liquors or solutions, starch, proteinaceous materials, acrylic latex paint emulsions, and textiles. The various temperatures at which such materials or products are manufactured, stored, or used as well as their intrinsic characteristics make them susceptible to growth, attack, and degradation by common microorganisms such as algae, fungi, yeasts, and bacteria. These microorganisms may be introduced during a manufacturing or other industrial process, by exposure to air, tanks, pipes, equipment, and humans. They can also be introduced while using a material or product, for example, by multiple openings and reclosures of packages or from stirring or removing material with contaminated objects.
To control deterioration or degradation caused by microorganisms, various industrial microbicides are used. Workers in the trade have continued to seek improved biocides that have low toxicity, are cost effective, and are also capable of exhibiting a prolonged biocidal effect against a wide variety of microorganisms with regular use.
Aqueous systems are also highly subject to microbiological growth, attack, and degradation. These aqueous systems may be fresh, brackish or saltwater systems. Exemplary aqueous systems include, but are not limited to, latexes, surfactants, dispersants, stabilizers, thickeners, adhesives, starches, waxes, proteins, emulsifying agents, cellulose products, metal working fluids, cooling water, waste water, aqueous emulsions, aqueous detergents, coating compositions, paint compositions, and resins formulated in aqueous solutions, emulsions or suspensions. These systems frequently contain relatively large amounts of water and organic material causing them to be environments well-suited for microbiological growth and thus attack and degradation.
Microbiological degradation of aqueous systems may manifest itself as a variety of problems, such as loss of viscosity, gas formation, objectionable odors, decreased pH, emulsion breaking, color change, and gelling. Additionally, microbiological deterioration of aqueous systems can cause fouling of the related water-handling system, which may include cooling towers, pumps, heat exchangers, and pipelines, heating systems, scrubbing systems, and other similar systems.
Another objectionable phenomenon occurring in aqueous systems, particularly in aqueous industrial process fluids, is slime formation. Slime formation can occur in fresh, brackish or salt water systems. Slime consists of matted deposits of microorganisms, fibers and debris. It may be stringy, pasty, rubbery, tapioca-like, or hard, and may have a characteristic undesirable odor that is different from that of the aqueous system in which it formed. The microorganisms involved in its formation are primarily different species of spore-forming and nonspore-forming bacteria, particularly capsulated forms of bacteria which secrete gelatinous substances that envelop or encase the cells. Slime microorganisms also include filamentous bacteria, filamentous fungi of the mold type, yeast, and yeast-like organisms. Slime reduces yields in production and causes plugging, bulking, and other problems in industrial water systems.
Despite the existence of such microbicides, industry is constantly seeking more cost-effective technology which offers equal or better protection at lower cost and lower concentration. The concentration of conventional microbicides and the corresponding treatment costs for such use, can be relatively high. Important factors in the search for cost-effective microbicides include the duration of microbicidal effect, the ease of use and the effectiveness of the microbicide per unit weight.